Case-based methods adopt either implicitly or now more often explicitly a case ontology—that is, they regard the cases as having properties which cannot be accounted for solely in terms of the properties of their components. This distinguishes case-based methods from enumerative methods in conventional variable-based quantitative research whereby cases are understood as bundles of variables and the primary mode of investigation analyses the cases solely in terms of the properties of those variables. Both quantitative and qualitative methods can be deployed in case-based research, often together. The history of case-based methods is outlined with examples presented from a range of times and disciplines. Case-based approaches include both those which focus on the single particular case and those which deploy comparison across cases, with comparison often being directed towards the establishment of causal accounts. Case-based methods and frames of inquiry considered include historical investigation, ethnographies, qualitative comparative analysis, process tracing, and actor-network informed techniques. Particular attention is given to the use of case-based methods in applied social research in evaluation and related practises. Most contemporary case-based research is applied and very often done outside the formal academy by researchers and practitioners.